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rcsid[] and sccsid[] and copyright[] are essentially unmaintained (and
unmaintainable).  these days, people use source.  these id's do not provide
any benefit, and do hurt the small install media
(the 33,000 line diff is essentially mechanical)
ok with the idea millert, ok dms

/*	$OpenBSD: regexp.c,v 1.8 2009/10/27 23:59:46 deraadt Exp $	*/
/*	$NetBSD: regexp.c,v 1.3 1994/11/17 08:28:02 jtc Exp $	*/

/*
 * Copyright (c) 1980, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <ctype.h>
#include <stdlib.h>
#include <string.h>
#include "extern.h"

#define FALSE	0
#define TRUE	!(FALSE)
#define NIL	0

static void	expconv(void);

boolean	 x_escaped;	/* true if we are currently x_escaped */
char	*x_start;	/* start of string */
boolean	 l_onecase;	/* true if upper and lower equivalent */

#define makelower(c) (isupper((c)) ? tolower((c)) : (c))

/*  STRNCMP -	like strncmp except that we convert the
 *	 	first string to lower case before comparing
 *		if l_onecase is set.
 */

int
STRNCMP(char *s1, char *s2, int len)
{
	if (l_onecase) {
	    do
		if (*s2 - makelower(*s1))
			return (*s2 - makelower(*s1));
		else {
			s2++;
			s1++;
		}
	    while (--len);
	} else {
	    do
		if (*s2 - *s1)
			return (*s2 - *s1);
		else {
			s2++;
			s1++;
		}
	    while (--len);
	}
	return(0);
}

/*	The following routine converts an irregular expression to
 *	internal format.
 *
 *	Either meta symbols (\a \d or \p) or character strings or
 *	operations ( alternation or parenthesizing ) can be
 *	specified.  Each starts with a descriptor byte.  The descriptor
 *	byte has STR set for strings, META set for meta symbols
 *	and OPER set for operations.
 *	The descriptor byte can also have the OPT bit set if the object
 *	defined is optional.  Also ALT can be set to indicate an alternation.
 *
 *	For metasymbols the byte following the descriptor byte identifies
 *	the meta symbol (containing an ascii 'a', 'd', 'p', '|', or '(').  For
 *	strings the byte after the descriptor is a character count for
 *	the string:
 *
 *		meta symbols := descriptor
 *				symbol
 *
 *		strings :=	descriptor
 *				character count
 *				the string
 *
 *		operatins :=	descriptor
 *				symbol
 *				character count
 */

/*
 *  handy macros for accessing parts of match blocks
 */
#define MSYM(A) (*(A+1))	/* symbol in a meta symbol block */
#define MNEXT(A) (A+2)		/* character following a metasymbol block */

#define OSYM(A) (*(A+1))	/* symbol in an operation block */
#define OCNT(A) (*(A+2))	/* character count */
#define ONEXT(A) (A+3)		/* next character after the operation */
#define OPTR(A) (A+*(A+2))	/* place pointed to by the operator */

#define SCNT(A) (*(A+1))	/* byte count of a string */
#define SSTR(A) (A+2)		/* address of the string */
#define SNEXT(A) (A+2+*(A+1))	/* character following the string */

/*
 *  bit flags in the descriptor 
 */
#define OPT 1
#define STR 2
#define META 4
#define ALT 8
#define OPER 16

static char *ccre;	/* pointer to current position in converted exp*/
static char *ure;	/* pointer current position in unconverted exp */

char *
convexp(char *re)
{
    char *cre;		/* pointer to converted regular expression */

    /* allocate room for the converted expression */
    if (re == NIL)
	return (NIL);
    if (*re == '\0')
	return (NIL);
    cre = malloc (4 * strlen(re) + 3);
    ccre = cre;
    ure = re;

    /* start the conversion with a \a */
    *cre = META | OPT;
    MSYM(cre) = 'a';
    ccre = MNEXT(cre);

    /* start the conversion (its recursive) */
    expconv ();
    *ccre = 0;
    return (cre);
}

static void
expconv(void)
{
    char *cs;		/* pointer to current symbol in converted exp */
    char c;		/* character being processed */
    char *acs;		/* pointer to last alternate */
    int temp;

    /* let the conversion begin */
    acs = NIL;
    cs = NIL;
    while (*ure != NIL) {
	switch (c = *ure++) {

	case '\\':
	    switch (c = *ure++) {

	    /* escaped characters are just characters */
	    default:
		if (cs == NIL || (*cs & STR) == 0) {
		    cs = ccre;
		    *cs = STR;
		    SCNT(cs) = 1;
		    ccre += 2;
		} else 
		    SCNT(cs)++;
		*ccre++ = c;
		break;

	    /* normal(?) metacharacters */
	    case 'a':
	    case 'd':
	    case 'e':
	    case 'p':
		if (acs != NIL && acs != cs) {
		    do {
			temp = OCNT(acs);
			OCNT(acs) = ccre - acs; 
			acs -= temp;
		    } while (temp != 0);
		    acs = NIL;
		}
		cs = ccre;
		*cs = META;
		MSYM(cs) = c;
		ccre = MNEXT(cs);
		break;
	    }
	    break;
	    
	/* just put the symbol in */
	case '^':
	case '$':
	    if (acs != NIL && acs != cs) {
		do {
		    temp = OCNT(acs);
		    OCNT(acs) = ccre - acs;
		    acs -= temp;
		} while (temp != 0);
		acs = NIL;
	    }
	    cs = ccre;
	    *cs = META;
	    MSYM(cs) = c;
	    ccre = MNEXT(cs);
	    break;

	/* mark the last match sequence as optional */
	case '?':
	    if (cs)
	    	*cs = *cs | OPT;
	    break;

	/* recurse and define a subexpression */
	case '(':
	    if (acs != NIL && acs != cs) {
		do {
		    temp = OCNT(acs);
		    OCNT(acs) = ccre - acs;
		    acs -= temp;
		} while (temp != 0);
		acs = NIL;
	    }
	    cs = ccre;
	    *cs = OPER;
	    OSYM(cs) = '(';
	    ccre = ONEXT(cs);
	    expconv ();
	    OCNT(cs) = ccre - cs;		/* offset to next symbol */
	    break;

	/* return from a recursion */
	case ')':
	    if (acs != NIL) {
		do {
		    temp = OCNT(acs);
		    OCNT(acs) = ccre - acs;
		    acs -= temp;
		} while (temp != 0);
		acs = NIL;
	    }
	    cs = ccre;
	    *cs = META;
	    MSYM(cs) = c;
	    ccre = MNEXT(cs);
	    return;

	/* mark the last match sequence as having an alternate */
	/* the third byte will contain an offset to jump over the */
	/* alternate match in case the first did not fail */
	case '|':
	    if (acs != NIL && acs != cs)
		OCNT(ccre) = ccre - acs;	/* make a back pointer */
	    else
		OCNT(ccre) = 0;
	    *cs |= ALT;
	    cs = ccre;
	    *cs = OPER;
	    OSYM(cs) = '|';
	    ccre = ONEXT(cs);
	    acs = cs;	/* remember that the pointer is to be filles */
	    break;

	/* if its not a metasymbol just build a character string */
	default:
	    if (cs == NIL || (*cs & STR) == 0) {
		cs = ccre;
		*cs = STR;
		SCNT(cs) = 1;
		ccre = SSTR(cs);
	    } else
		SCNT(cs)++;
	    *ccre++ = c;
	    break;
	}
    }
    if (acs != NIL) {
	do {
	    temp = OCNT(acs);
	    OCNT(acs) = ccre - acs;
	    acs -= temp;
	} while (temp != 0);
	acs = NIL;
    }
    return;
}
/* end of converter */


/*
 *	The following routine recognises an irregular expression
 *	with the following special characters:
 *
 *		\?	-	means last match was optional
 *		\a	-	matches any number of characters
 *		\d	-	matches any number of spaces and tabs
 *		\p	-	matches any number of alphanumeric
 *				characters. The
 *				characters matched will be copied into
 *				the area pointed to by 'name'.
 *		\|	-	alternation
 *		\( \)	-	grouping used mostly for alternation and
 *				optionality
 *
 *	The irregular expression must be translated to internal form
 *	prior to calling this routine
 *
 *	The value returned is the pointer to the first non \a 
 *	character matched.
 */

char *
expmatch(char *s, char *re, char *mstring)
{
    char *cs;			/* the current symbol */
    char *ptr,*s1;		/* temporary pointer */
    boolean matched;		/* a temporary boolean */

    /* initial conditions */
    if (re == NIL)
	return (NIL);
    cs = re;
    matched = FALSE;

    /* loop till expression string is exhausted (or at least pretty tired) */
    while (*cs) {
	switch (*cs & (OPER | STR | META)) {

	/* try to match a string */
	case STR:
	    matched = !STRNCMP (s, SSTR(cs), SCNT(cs));
	    if (matched) {

		/* hoorah it matches */
		s += SCNT(cs);
		cs = SNEXT(cs);
	    } else if (*cs & ALT) {

		/* alternation, skip to next expression */
		cs = SNEXT(cs);
	    } else if (*cs & OPT) {

		/* the match is optional */
		cs = SNEXT(cs);
		matched = 1;		/* indicate a successful match */
	    } else {

		/* no match, error return */
		return (NIL);
	    }
	    break;

	/* an operator, do something fancy */
	case OPER:
	    switch (OSYM(cs)) {

	    /* this is an alternation */
	    case '|':
		if (matched)

		    /* last thing in the alternation was a match, skip ahead */
		    cs = OPTR(cs);
		else

		    /* no match, keep trying */
		    cs = ONEXT(cs);
		break;

	    /* this is a grouping, recurse */
	    case '(':
		ptr = expmatch (s, ONEXT(cs), mstring);
		if (ptr != NIL) {

		    /* the subexpression matched */
		    matched = 1;
		    s = ptr;
		} else if (*cs & ALT) {

		    /* alternation, skip to next expression */
		    matched = 0;
		} else if (*cs & OPT) {

		    /* the match is optional */
		    matched = 1;	/* indicate a successful match */
		} else {

		    /* no match, error return */
		    return (NIL);
		}
		cs = OPTR(cs);
		break;
	    }
	    break;

	/* try to match a metasymbol */
	case META:
	    switch (MSYM(cs)) {

	    /* try to match anything and remember what was matched */
	    case 'p':
		/*
		 *  This is really the same as trying the match the
		 *  remaining parts of the expression to any subset
		 *  of the string.
		 */
		s1 = s;
		do {
		    ptr = expmatch (s1, MNEXT(cs), mstring);
		    if (ptr != NIL && s1 != s) {

			/* we have a match, remember the match */
			strncpy (mstring, s, s1 - s);
			mstring[s1 - s] = '\0';
			return (ptr);
		    } else if (ptr != NIL && (*cs & OPT)) {

			/* it was optional so no match is ok */
			return (ptr);
		    } else if (ptr != NIL) {

			/* not optional and we still matched */
			return (NIL);
		    }
		    if (!isalnum(*s1) && *s1 != '_')
			return (NIL);
		    if (*s1 == '\\')
			x_escaped = x_escaped ? FALSE : TRUE;
		    else
			x_escaped = FALSE;
		} while (*s1++);
		return (NIL);

	    /* try to match anything */
	    case 'a':
		/*
		 *  This is really the same as trying the match the
		 *  remaining parts of the expression to any subset
		 *  of the string.
		 */
		s1 = s;
		do {
		    ptr = expmatch (s1, MNEXT(cs), mstring);
		    if (ptr != NIL && s1 != s) {

			/* we have a match */
			return (ptr);
		    } else if (ptr != NIL && (*cs & OPT)) {

			/* it was optional so no match is ok */
			return (ptr);
		    } else if (ptr != NIL) {

			/* not optional and we still matched */
			return (NIL);
		    }
		    if (*s1 == '\\')
			x_escaped = x_escaped ? FALSE : TRUE;
		    else
			x_escaped = FALSE;
		} while (*s1++);
		return (NIL);

	    /* fail if we are currently x_escaped */
	    case 'e':
		if (x_escaped)
		    return(NIL);
		cs = MNEXT(cs); 
		break;

	    /* match any number of tabs and spaces */
	    case 'd':
		ptr = s;
		while (*s == ' ' || *s == '\t')
		    s++;
		if (s != ptr || s == x_start) {

		    /* match, be happy */
		    matched = 1;
		    cs = MNEXT(cs); 
		} else if (*s == '\n' || *s == '\0') {

		    /* match, be happy */
		    matched = 1;
		    cs = MNEXT(cs); 
		} else if (*cs & ALT) {

		    /* try the next part */
		    matched = 0;
		    cs = MNEXT(cs);
		} else if (*cs & OPT) {

		    /* doesn't matter */
		    matched = 1;
		    cs = MNEXT(cs);
		} else

		    /* no match, error return */
		    return (NIL);
		break;

	    /* check for end of line */
	    case '$':
		if (*s == '\0' || *s == '\n') {

		    /* match, be happy */
		    s++;
		    matched = 1;
		    cs = MNEXT(cs);
		} else if (*cs & ALT) {

		    /* try the next part */
		    matched = 0;
		    cs = MNEXT(cs);
		} else if (*cs & OPT) {

		    /* doesn't matter */
		    matched = 1;
		    cs = MNEXT(cs);
		} else

		    /* no match, error return */
		    return (NIL);
		break;

	    /* check for start of line */
	    case '^':
		if (s == x_start) {

		    /* match, be happy */
		    matched = 1;
		    cs = MNEXT(cs);
		} else if (*cs & ALT) {

		    /* try the next part */
		    matched = 0;
		    cs = MNEXT(cs);
		} else if (*cs & OPT) {

		    /* doesn't matter */
		    matched = 1;
		    cs = MNEXT(cs);
		} else

		    /* no match, error return */
		    return (NIL);
		break;

	    /* end of a subexpression, return success */
	    case ')':
		return (s);
	    }
	    break;
	}
    }
    return (s);
}